<template lang="pug">
    div#app
      canvas#canvas
      div#background
        img(src="./assets/image/starry_sky_background.jpg")
        div#content
          div#personCenter
            img(src="./assets/image/person_center.png")
          div#setting
            img(src="./assets/image/setting.png" @click="returnHome")
          router-view
</template>

<script>
export default {
    mounted() {
        //宇宙特效
        var canvas = document.getElementById("canvas"),
            ctx = canvas.getContext("2d"),
            w = (canvas.width = window.innerWidth),
            h = (canvas.height = window.innerHeight),
            hue = 217,
            stars = [],
            count = 0,
            maxStars = 1300; //星星数量
        var canvas2 = document.createElement("canvas"),
            ctx2 = canvas2.getContext("2d");
        canvas2.width = 100;
        canvas2.height = 100;
        var half = canvas2.width / 2,
            gradient2 = ctx2.createRadialGradient(
                half,
                half,
                0,
                half,
                half,
                half
            );
        gradient2.addColorStop(0.025, "#CCC");
        gradient2.addColorStop(0.1, "hsl(" + hue + ", 61%, 33%)");
        gradient2.addColorStop(0.25, "hsl(" + hue + ", 64%, 6%)");
        gradient2.addColorStop(1, "transparent");
        ctx2.fillStyle = gradient2;
        ctx2.beginPath();
        ctx2.arc(half, half, half, 0, Math.PI * 2);
        ctx2.fill();
        // End cache
        function random(min, max) {
            if (arguments.length < 2) {
                max = min;
                min = 0;
            }
            if (min > max) {
                var hold = max;
                max = min;
                min = hold;
            }
            return Math.floor(Math.random() * (max - min + 1)) + min;
        }
        function maxOrbit(x, y) {
            var max = Math.max(x, y),
                diameter = Math.round(Math.sqrt(max * max + max * max));
            return diameter / 2;
            //星星移动范围，值越大范围越小，
        }
        var Star = function() {
            this.orbitRadius = random(maxOrbit(w, h));
            this.radius = random(60, this.orbitRadius) / 8;
            //星星大小
            this.orbitX = w / 2;
            this.orbitY = h / 2;
            this.timePassed = random(0, maxStars);
            this.speed = random(this.orbitRadius) / 50000;
            //星星移动速度
            this.alpha = random(2, 10) / 10;
            count++;
            stars[count] = this;
        };
        Star.prototype.draw = function() {
            var x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX,
                y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY,
                twinkle = random(10);
            if (twinkle === 1 && this.alpha > 0) {
                this.alpha -= 0.05;
            } else if (twinkle === 2 && this.alpha < 1) {
                this.alpha += 0.05;
            }
            ctx.globalAlpha = this.alpha;
            ctx.drawImage(
                canvas2,
                x - this.radius / 2,
                y - this.radius / 2,
                this.radius,
                this.radius
            );
            this.timePassed += this.speed;
        };
        for (var i = 0; i < maxStars; i++) {
            new Star();
        }
        function animation() {
            ctx.globalCompositeOperation = "source-over";
            ctx.globalAlpha = 0.5; //尾巴
            ctx.fillStyle = "hsla(" + hue + ", 64%, 6%, 2)";
            ctx.fillRect(0, 0, w, h);
            ctx.globalCompositeOperation = "lighter";
            for (var i = 1, l = stars.length; i < l; i++) {
                stars[i].draw();
            }
            window.requestAnimationFrame(animation);
        }
        animation();
    },
    methods: {
        returnHome() {
            this.$router.push({ path: "/" });
        }
    }
};
</script>


<style lang="scss">
@import "./assets/style/reset.css";
@import "./assets/style/ele.scss";
$distance: 30px;
%img {
    width: 30px;
    height: 30px;
}
%curios {
    cursor: pointer;
}
%screen {
    width: 100%;
    height: 100%;
}
#app {
    width: 100vw;
    height: 100vh;
    overflow: hidden;
    position: absolute;
}
#canvas {
    @extend %screen;
    position: absolute;
    z-index: 1;
}
#background {
    @extend %screen;
    position: absolute;
    & > img {
        @extend %screen;
        position: absolute;
        z-index: 2;
        opacity: 0.4;
    }
}
#content {
    position: relative;
    z-index: 3;
    @extend %screen;
    color: white;
}
#personCenter {
    position: fixed;
    top: $distance;
    left: $distance;
    @extend %curios;
    & > img {
        @extend %img;
    }
}
#setting {
    position: fixed;
    top: $distance;
    right: $distance;
    @extend %curios;
    & > img {
        @extend %img;
    }
}
</style>
